(1) Field of the Invention
The present invention relates to a method and system for depositing functionally graded materials onto a substrate using a cold spray deposition technique.
(2) Prior Art
Cold gas dynamic spraying or “cold spray” has been recently introduced as a new metallization spray technique to deposit powder metal without inclusions onto a substrate. A supersonic jet of helium and/or nitrogen is formed by a converging/diverging nozzle and is used to accelerate the powder particles toward the substrate to produce cold spray deposits or coatings. Deposits adhere to the substrate and previously deposited layers through plastic deformation and bonding. U.S. Pat. Nos. 5,302,414 and 6,502,767 illustrate cold gas dynamic spraying techniques.
Currently, bond coats are applied using low pressure plasma spray (LPPS). Operation and maintenance of LPPS systems is expensive and time consuming, limiting throughput. Also, LPPS requires a vacuum chamber. The size of a given chamber limits the size of the parts that can be processed.
Recently, it has been suggested by the applicants to use “cold spray” to apply a bond coat to engine components. A system and a method for applying such a bond coat is shown in co-pending U.S. patent application Ser. No. 11/088,380, filed Mar. 23, 2005 now abandoned, entitled Applying Bond Coat to Engine Components Using Cold Spray.
Due to engine operating temperatures, strength requirements, and the like, material changes are required along the axial length of the engine. Typically, this means that separate components, each constructed from a different material, are fabricated and then bolted or welded together. In some instances, due to incompatibility between the two materials, welding cannot even be considered and bolting is the only option.